In a new study, terrestrial bacteria-infecting viruses were still able to infect their E. coli hosts in near-weightless "microgravity" conditions aboard the International Space Station, but the dynamics of virus-bacteria interactions differed from those observed on Earth. Interactions between phages -- viruses that infect bacteria -- and their hosts play an integral role in microbial ecosystems. However, few studies have explored the specifics of how phage-bacteria dynamics differ in microgravity. To address that gap, Huss and colleagues compared two sets of bacterial E. coli samples infected with a phage known as T7 -- one set incubated on Earth and the other aboard the International Space Station. The space-station phages gradually accumulated specific mutations that could boost phage infectivity or their ability to bind receptors on bacterial cells. Meanwhile, the space-station E. coli accumulated mutations that could protect against phages and enhance survival success in near-weightless conditions. The researchers then applied a high-throughput technique known as deep mutational scanning to more closely examine changes in the T7 receptor binding protein, which plays a key role in infection, revealing further significant differences between microgravity versus Earth conditions. Additional experiments on Earth linked these microgravity-associated changes in the receptor binding protein to increased activity against E. coli strains that cause urinary tract infections in humans and are normally resistant to T7. Overall, this study highlights the potential for phage research aboard the ISS to reveal new insights into microbial adaption, with potential relevance to both space exploration and human health. The authors add, "Space fundamentally changes how phages and bacteria interact: infection is slowed, and both organisms evolve along a different trajectory than they do on Earth. By studying those space-driven adaptations, we identified new biological insights that allowed us to engineer phages with far superior activity against drug-resistant pathogens back on Earth." Citation: Huss P, Chitboonthavisuk C, Meger A, Nishikawa K, Oates RP, Mills H, et al. (2026) Microgravity reshapes bacteriophage-host coevolution aboard the International Space Station. Author countries: United StatesFunding: This work was supported by the Defense Threat Reduction Agency (https://www.dtra.mil/) (Grant HDTRA1-16-1-0049) to S.R. was supported by a graduate training scholarship from the Anandamahidol Foundation (Thailand). Scientists Develop IV Therapy That Repairs the Brain After Stroke Stay informed with ScienceDaily's free email newsletter, updated daily and weekly. Keep up to date with the latest news from ScienceDaily via social networks: Tell us what you think of ScienceDaily -- we welcome both positive and negative comments.